Apparatus and method especially useful in label making

ABSTRACT

Imaging apparatus featuring a source of light including a flashtube for exposing through an imaging master an imaging medium responsive to light to produce an image of color density dependent upon the quantity of light to which the medium is exposed; and a control arranged to deliver to the flashtube for each image desired a series of electrical pulses to produce a corresponding series of flashes, to limit the energy level of each pulse to a fraction of the recommended energy input of the flashtube, spacing the pulses sufficiently closely in time so that there is heat buildup with successive pulses and further series of pulses may be closely enough spaced following earlier series to produce further heat buildup, making possible a total number of images, a density of images, and a frequency of image making capability of which the flashtube would be incapable if it were pulsed a single time for each image.

United States Patent [1 1 White et al.

[ APPARATUS AND METHOD ESPECIALLY USEFUL IN LABEL MAKING [75] Inventors: Roby Byron White, Cumberland,

R.l.; Frederic Samuel Tobey, Hyde Park, Mass.

[73] Assignee: W. H. Brady Co., Milwaukee, Wis.

[22] Filed: Apr. 2, 1973 [21] Appl. N0.: 346,880

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 122,764, March 10,

1971, abandoned.

[ May6, 1975 3,698,296 10/1972 Heuser 95/4.5 R

Primary Examiner-Samuel S. Matthews Assistant ExaminerAlan Mathews [5 7] ABSTRACT Imaging apparatus featuring a source of light including a flashtube for exposing through an imaging master an imaging medium responsive to light to produce an image of color density dependent upon the quantity of light to which the medium is exposed; and a control arranged to deliver to the flashtube for each image desired a series of electrical pulses to produce a corresponding series of flashes, to limit the energy level of each pulse to a fraction of the recommended energy input of the flashtube, spacing the pulses sufficiently closely in time so that there is heat buildup with successive pulses and further series of pulses may be closely enough spaced following earlier series to produce further heat buildup, making possible a total number of images, a density of images, and a frequency of image making capability of which the flashtube would be incapable if it were pulsed a single time for each image.

6 Claims, 4 Drawing Figures mgmgum-r sms 3881.821

sum 10? 2 FIG I PATENTEBNH 6&975

SHEET 2 BF 2 APPARATUS AND METHOD ESPECIALLY USEFUL IN LABEL MAKING RELATED APPLICATIONS This application is a continuation in part of our U.S. Pat. Application Ser. No. 122,764, Flashing, filed Mar. 10, 1971, now abandoned. Circuitry shown herein is the subject of our copending U.S. Pat. Application Ser. No. 270,659, Flashing Circuitry, which was granted on Oct. 23, 1973 as U.S. Pat. No. 3,767,969. Subject matter disclosed herein relating to positioning a cartridge and to a low friction back-up tab was the sole invention of Frederic S. Tobey, and the subject of his copending U.S. Pat. Application Ser. No. 122,929, Web Processing Cartridges, filed May 10, 1971, which was granted on July 24, 1973 as U.S. Pat. No. 3,747,865.

BACKGROUND OF THE INVENTION This invention relates to photographically creating, with a flashtube, an image on an imaging medium (e.g. in a label maker).

Ultraviolet imaging paper (available from E. I. du- Pont de Nemours under the trade designation Dylux) is known to be sensitive to ultraviolet light to produce an image having color density depending upon the quantity of ultraviolet energy reaching the paper, that quantity in turn depending upon the light intensity and total exposure time in one or more exposures.

F lashtubes are sold with ratings which relate to the level of energy input to the tube. Among these are the explosion energy (the per flash input energy level which will cause the tube to explode within ten flashes) and the recommended energy input (typically a per flash input level of 40-50 percent of explosion energy) at which the tube life will extend over several thousand flashes.

Producing images using more than a single flash of light per image is not, stated that broadly, new. Hoekstra U.S. Pat. No. 2,829,315 adverts to pulsing a film projector lamp (one or more light flashes during each image of the film, col. 1, lines 22-23). Japanese Patent No. 39-391 discloses use of multiple flashes in a photographic printer, to change print gradation; up to 50 flashes per print is disclosed, and it is said that emission intensity is adjusted in reciprocal proportion to the emission times. Ludloff German Patent No. l 225 041 discloses improving photographic printing of density by using a multiplicity of extremely short and intense light flashes per image. Creedon et al. U.S. Pat. No. 3,634,084 discloses use of multiple low-intensity discrete light flashes to mitigate formation of spurious exposed areas.

However, so far as we are aware, it has not been taught than an amount and frequency of exposure of which a flashtube would otherwise be incapable without failure can be achieved through use of a multiplicity of lower energy flashes.

SUMMARY OF THE INVENTION In general the invention features a source of light including a flashtube for exposing through an imaging master an imaging medium responsive to light to produce an image of color density dependent upon the quantity of light to which the medium is exposed; and a control arranged to deliver to the flashtube for each image desired a series of electrical pulses to produce a corresponding series of flashes, to limit the energy level of each pulse to a fraction of the recommended energy input of the flashtube, spacing the pulses sufficiently closely in time so that there is heat buildup with successive pulses and further series of pulses may be closely enough spaced following earlier series to produce further heat buildup, making possible a total number of images, a density of images, and a frequency of image making capability of which the flashtube would be incapable if it were pulsed a single time for each image. In preferred embodiments an index is provided for advancing successive portions of an ultraviolet imaging medium to an imaging position aligned with the light source; and the control includes a switch and circuitry arranged to deliver at least 4 (and preferably at least 20) pulses between successive actuations of the switch.

The invention thus permits the use of inexpensive, small bore, low pressure flashtubes, for exposing successive images in rapid sequence, while providing simple and reliable operation and dark images, with greatly improved freedom from crazing, bending, ballooning, or extreme darkening of the tube envelope, and loss of pressure in the tube.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of a fragment of the processor;

FIG. 2 is an enlargement of a fragment of a tape cartridge of width different from that shown in FIG. 1;

FIG. 3 is a sectional view taken at to the section of FIG. 1; and

FIG. 4 is a schematic drawing of electrical circuitry for pulsing the flashtube.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, label making apparatus is shown in which a circular master stencil 10 is mounted between xenon arc flashtube 12 and cartridge 14 of ultraviolet imaging tape 16 (coated with a material sold by E. I. duPont de Nemours under the trade designation Dylux). The cartridge is of opaque plastic, has a side wall 18 from which protrude three identical exterior lugs 20, and has a tape guide 22 of inside width barely larger than the width of the tape. Secured to mounting bracket 24 is a post 26 which fits through opening 28 to support the cartridge with lugs 20 against bracket wall surface 30. The lugs are equally spaced angularly about opening 28 to vertically orient the cartridge, and are kept in contact with surface 20 by springs 32 on post 26.

Knurled tape indexing wheel 40 is carried by shaft 42 and presses against tape 16 through opening 44 in guide 22. A back-up tab 46 of Teflon is fixed to the inner guide surface opposite opening 44, to allow tape 16 to slide smoothly through the guide as wheel 40 rotates. Finger operated lever 48 is provided to rotate shaft 42 through conventional linkage (not shown).

Tape 16 extends from guide 22 to an imaging station 50 beneath aperture 52 at the bottom of flashtube housing 54. Filter 56 covers aperture 52 to screen out all light except that in the ultraviolet frequency range.

Stencil 10 is opaque except for characters (e.g., at 58) arranged along its periphery. The stencil can be rotated about axis 60 to bring a selected character into registry with flashtube l2.

An electrical circuit (shown in detail in FIG. 4), including switch 70 mounted beneath lever 48 of the index mechanism, is arranged to supply to flashtube 12, upon each actuation of switch 70, a rapid series (over a total period of about 400 milliseconds) of 25 electrical pulses each of 1.56 joules energy level (less than 5 percent of explosion energy) and 200 microseconds duration.

The cartridge shown in FIG. 2 is identical to that of FIGS. 1 and 3 except that guide 22 is wider than guide 22 (to accommodate a wider tape, omitted from FIG. 2), and lugs 20. are correspondingly shorter, so that the distance X between the ends of the lugs and the centerline of the tape guide is the same for'all cartridges.

In use, a cartridge with tape of the desired width is loaded on post 26. With lugs 20 or 20' against surface 30, the centerline of guide 22 or 22' and hence the centerline of the tape, will be centered under aperture 52, whatever the width of the tape. To make a label, stencil (or imaging master) is rotated to bring the desired character to imaging station 50, and lever 48 is depressed to close switch 7 0, causing flashtube 12 to flash 25 times as the 25 pulses described above are delivered. After exposure, lever 48 is released, rotating wheel 40 to advance tape 16. (Or, the tape can be advanced prior to imaging.) Successive characters are similarly imaged on the tape. Upon exposure to visible light the images on the tape become photographically fixed.

The low energy level (relative to explosion energy) pulsing of the tube prevents crazing, bending, ballooning, or extreme darkening of the flashtube envelope, or pressure loss, over a tube life of often millions of flashes, even though the total energy supplied in each series of flashes which make up each character exposure equals a large amount and not only the flashes but as well successive series of flashes follow each other so rapidly that there is build-up of heat. At the same time, the total energy level of each character exposure is sufficient to give a dark image.

Image darkness can be controlled by varying the number of flashes per exposure.

The electrical circuitry for actuating the flashtube is shown in FIG. 4, and in general consists of a main energy circuit 100 for providing a series of flashes, timed in accordance with the frequency (50-60 Hz) of the AC line current applied through lines 102 and 104, a firing circuit 106 for firing the flashtube under the control'of circuit 100, and a total cycle timing circuit 108 for terminating the series of flashes after the flashtube has fired the desired number of times.

In circuit 100, capacitor 110 (58 mfd) is charged during each AC cycle, which provides the energy to trigger circuit 106. In particular, when switch 70 (single pole double throw) is depressed (as shown in FIG. 4) line current charges capacitor 112 (400 mfd) to near peak line voltage through resistor 114 (10 Ohm) and diode 116 during the first quarter of the AC cycle. During the second and third quarters of the AC cycle the voltage at junction 1 18 rises to approximately twice peak voltage (the sum of the reversed line voltage and that already present across capacitor 112), SCR 120 is turned on (and is kept on by 16K resistor 122), and a portion of the charge on capacitor 112 transfers to capacitor 110 (the ratio of charges of the two capacitors being in inverse proportion to the ratio of capacitances, so that the smaller capacitor 110 will be charged to 4 above peak line voltage). Resistors 124 (100K) and 126 (220K) are bleed resistors to discharge capacitors 120 and 110 for safety purposes when the unit is turned off. Resistor 128 (6.8K) and diode 130 work in con- 5 junction with circuit 108 as described below.

While capacitor 110 is being charged as just described it in turn charges, in circuit 106, capacitor 132 (0.33 mfd) through resistor 134 (3.3K), and capacitor 136 (0.022 mfd) through resistor 138 (1.2 meg). When charged to approximately volts, capacitor 136 fires neon tube 140, turning on SCR 142. As a result, capacitor 132 discharges into the primary of stepup transformer 144. The voltage across the transformer secondary then fires flashtube 12. The current through the flashtube causes SCR 142 to be reset. Ground reference resistor 146 (470 Ohms) prevents false firing of SCR 142.

During each flash-producing discharge of capacitor current also flows through diode 130, resistor 150 (680 ohms), diode 152, thermistor 153, zener diode 154 (V), and resistor 156 (chosen to give the desired charging rate of capacitor 158, and hence the desired number of flashes per exposure), to charge capacitor 158 (0.1 mfd). Diode 152 prevents current leak from capacitor 158 between flashes, so that the voltage across capacitor 158 increases upon each flash, and eventually fires neon tube 160, turning on SCR 162 and causing discharge of capacitor 110, terminating the series of flashes. The voltage drop across diode causes SCR 120 to turn off, and the continuing current flow through resistor 128 and diode 130 from capacitor 112 holds SCR 120 in its off condition. Resistor 156 controls the rate of charge of capacitor 158, hence determining the number of flashes per exposure. Zener diode 154 provides a threshold voltage below which current will not flow to capacitor 158, so that capacitor 158 charges during only a small peak portion of each AC cycle. As a result, the charge rate of capacitor 158 is sensitive to fluctuations in line voltage, so that the number of flashes per exposure will drop as line voltage increases, tending to equalize total energy supplied to the flashtube per exposure.

The thermistor 153 compensates for the fact that, even at unchanging line voltage, more energy is delivered per pulse as the components, in particular the capacitors 110 and 112, warm up. The thermistor 153, which is mounted in heat transfer relationship with capacitor 110, provides decreased resistance as capacitor 110 heats up, thus charging capacitor 158 a greater amount on each pulse, and thus diminishing the number of pulses in a way compensating for the increased energy per pulse owing to temperature increase.

Resistor 164 (470 ohms) prevents false firing of SCR 162.

When switch 70 is released capacitor 158 is discharged by the normally closed contacts of switch 70, so that the next exposure cycle will be of the same length. 1

A centrifugal 3 7/16 inch diameter fan (not shown) 7 is mounted to blow cooling air over the electrical circuitry and flashtube.

Other embodiments are within the following claims.

What is claimed is:

1. Imaging apparatus for delivery of light energy at a predetermined continuing rate (joules/unit time) for a predetermined length of time to produce images of a predetermined density at a predetermined rate which comprises:

means to position an imaging medium responsive to light, to produce an image of density dependent upon the quantity of light to which said medium is exposed,

a source of light including a flashtube positioned for exposing said imaging medium, said flashtube being of energy rating low relative to the energy required to produce said images,

an imaging master located relative to said imaging medium and said flashtube so that light energy emanating from said flashtube amd impinging on said imaging medium is modified by said imaging master to produce an image in said imaging medium responsive to said imaging master and said flashtube, and

circuitry control means for providing a series of lower energy level pulses to said flashtube for each said image, to produce a corresponding number of flashes of said light energy, the total quantity of light energy delivered to said imaging medium in said series being sufficient to produce said density,

said circuitry control means being further characterized in that successive series may be initiated rapidly enough to produce further heat buildup from one series to the next.

2. The apparatus of claim 1 which includes filter means positioned between said flashtube and said imaging medium to screen out from the spectrum of energy emitted by said flashtube a portion of said spectrum.

3. The apparatus of claim 2 wherein said imaging medium is responsive to ultraviolet light to produce an image of density dependent upon the quantity of ultraviolet light to which said medium is exposed, and said source is a source of ultraviolet light.

4. The apparatus of claim 3 wherein said circuitry control means include a switch and circuitry means to deliver a said series upon an actuation of said switch.

5. The apparatus of claim 4 wherein said series includes at least four pulses.

6. The apparatus of claim 5 wherein said series includes at least 20 said pulses. 

1. Imaging apparatus for delivery of light energy at a predetermined continuing rate (joules/unit time) for a predetermined length of time to produce images of a predetermined density at a predetermined rate which comprises: means to position an imaging medium responsive to light, to produce an image of density dependent upon the quantity of light to which said medium is exposed, a source of light including a flashtube positioned for exposing said imaging medium, said flashtube being of energy rating low relative to the energy required to produce said images, an imaging master located relative to said imaging medium and said flashtube so that light energy emanating from said flashtube amd impinging on said imaging medium is modified by said imaging master to produce an image in said imaging medium responsive to said imaging master and said flashtube, and circuitry control means for providing a series of lower energy level pulses to said flashtube for each said image, to produce a corresponding number of flashes of said light energy, the total quantIty of light energy delivered to said imaging medium in said series being sufficient to produce said density, said circuitry control means being further characterized in that successive series may be initiated rapidly enough to produce further heat buildup from one series to the next.
 2. The apparatus of claim 1 which includes filter means positioned between said flashtube and said imaging medium to screen out from the spectrum of energy emitted by said flashtube a portion of said spectrum.
 3. The apparatus of claim 2 wherein said imaging medium is responsive to ultraviolet light to produce an image of density dependent upon the quantity of ultraviolet light to which said medium is exposed, and said source is a source of ultraviolet light.
 4. The apparatus of claim 3 wherein said circuitry control means include a switch and circuitry means to deliver a said series upon an actuation of said switch.
 5. The apparatus of claim 4 wherein said series includes at least four pulses.
 6. The apparatus of claim 5 wherein said series includes at least 20 said pulses. 